1. Field of the Invention
The present invention relates to an optical/optomagnetic disk apparatus for driving an optical disk and/or an optomagnetic disk which can be read/write accessed any number of times and for performing read/write access. More particularly, the present invention relates to improvements of a mechanism for opening/closing a shutter of a cartridge which stores a disk, and a mechanism for moving a magnet for applying an external magnetic field during read/write access of the optomagnetic disk.
2. Description of the Related Art
An optical disk has advantages in that information can be recorded at a high density, the disk is almost free from noise, and the disk is not brought into mechanical contact with a head. However, the optical disk has disadvantages in that information written therein cannot be erased and information cannot be written therein again.
In order to overcome the above disadvantages, an optomagnetic disk capable of performing erase and write operations any number of times has been developed. This optomagnetic disk is stored in and protected by a cartridge in the same manner as in the optical disk. An openable shutter is arranged in the cartridge. The shutter is opened/closed by a shutter opening/closing mechanism incorporated in the optomagnetic disk apparatus, and an erase, read, or write operation is performed. However, an external magnetic field must be applied to the optomagnetic disk at the time of the erase or write operation. For this purpose, a magnet unit must be arranged in the optomagnetic disk apparatus to apply an external magnetic field to the disk. In the optomagnetic disk apparatus, the magnet unit must be arranged, and an exclusive structure for moving the magnet unit is required. Therefore, a conventional optical disk apparatus cannot be employed without modifications.
The reason why the exclusive structure is required in the optomagnetic apparatus will be described. The structure of an optical apparatus disclosed in Japanese Patent Application No. 61-137480 as an example of the conventional optical disk apparatus will be described with reference to FIGS. 1 to 4.
In order to improve operability of the apparatus and protect the optical disk, the cartridge which stores the optical disk therein can be inserted in the apparatus. A shutter opening/closing mechanism for automatically opening/closing the shutter of the cartridge is incorporated in the apparatus.
Reference symbol a denotes a cartridge which stores an optical disk as an information recording medium; and b, a cartridge holder for holding the cartridge a. The cartridge holder b can be moved in an insertion direction.
A cam plate d is pivotally mounted on the cartridge holder b through a cam plate center-of-rotation pin c. A substantially elliptical groove e is formed in the cam plate d. A cam plate drive/fixing pin f arranged on a stationary member is engaged in the groove e. The cam plate d is pivoted about the pin c serving as the center of rotation of the cam plate d upon movement of the cartridge holder b.
Shutter openers (schematically illustrated) k for sides A and B are arranged in the cartridge holder b. Drive pins g which can engage with a guide groove h and guide pins m which can engage with a guide groove n extend on the shutter openers k, respectively. The shutter openers k are movable in the opening/closing direction of the shutter i. The shutter openers k have an engaging portion (not shown) engaged with a groove n formed in the shutter i. The drive pins g integral with the shutter openers k are interlocked with pivotal movement of the cam plate d. One of the shutter openers k is moved depending on side A or B of the cartridge a, thereby opening/closing the shutter i.
Note that reference symbol o denotes a cam plate fixing pin.
The cartridge a is inserted from a cartridge insertion/ejection port (not shown) of the apparatus to a predetermined position. The cartridge a is held by the cartridge holder b, as shown in FIG. 2. At this time, snapper seats b formed on side end faces of the cartridge p are engaged with snappers (not shown) incorporated in the cartridge a. Therefore, the cartridge a is firmly held in the cartridge holder b and the cam plate d is slightly pivoted clockwise.
When the cartridge holder b is moved in a direction for causing a holder moving mechanism (not shown) to receive the cartridge holder b, the cam plate drive/ fixing pin f is moved within the groove e of the cam plate d, as shown in FIG. 3. The cam plate d is pivoted about the cam plate center-of-rotation pin c and is moved to the position shown in FIG. 4.
Upon pivotal movement of the cam plate d, one drive pin g is moved to the right, and the corresponding shutter opener k is moved to the right. Therefore, the shutter i is open by about 40 mm in a direction perpendicular to the insertion direction of the cartridge holder a.
In order to eject the cartridge holder a, operations are performed in the reversed order, and the shutter i is closed. The shutter opening/closing mechanism of the cartridge of the conventional optical disk uses the cam plate d for opening/closing the shutter.
In the conventional shutter opening/closing mechanism using the cam plate, when a magnet unit for generating a write/erase magnetic field is arranged, the magnet unit must be arranged at the position of the shutter opening/closing cam plate due to the limitations of component layout.
For this reason, the magnet unit for generating the write/erase magnetic field cannot oppose the optomagnetic disk due to the presence of the cam plate. Therefore, the above arrangement cannot be directly employed in the optomagnetic disk apparatus.
There is much room for improving a support structure of the magnet unit. Support structures of the magnet unit are disclosed in Japanese Patent Disclosure (Kokai) Nos. 62-8345, 62-14352, and 61-222001. Round and square rod-like permanent magnets are used as magnet units in optomagnetic disk apparatuses. In this case, in order to obtain a sufficient magnetic field on an optomagnetic disk mounted on a turntable, the magnet unit must oppose the optomagnetic disk in a proximate state. However, when the magnet unit opposes the optomagnetic disk in a proximate state, the cartridge of the optomagnetic disk abuts against part of the magnet unit during insertion of the optomagnetic disk into the magnetic disk apparatus. There is then a fear of damaging the magnet unit and the cartridge. In a conventional arrangement, a magnet unit moving mechanism is arranged and the entire magnet unit is retracted from the moving path of the cartridge of the optomagnetic disk to a standby position, thereby preventing interference between the cartridge of the optomagnetic disk and the magnet unit. In the write or erase mode, the magnet unit is moved from the standby position to a predetermined set position. However, the presence of the magnet unit moving mechanism undesirably results in a bulky optomagnetic disk apparatus.
According to another conventional proposal, a strong magnetic field is generated by using a magnet consisting of a rare earth element to increase a distance between the optomagnetic disk and the set position of the magnet unit in the write or erase mode. Abutment of the cartridge of the optomagnetic disk during insertion or ejection of the optomagnetic disk into or from the optomagnetic disk apparatus can be prevented. In this case, however, a relatively expensive rare earth element must be used, thus resulting in high cost.